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Greenhouse misconceptions

May 11, 2020
Common Cannabis Questions

10 Misconceptions About Growing Marijuana in a Greenhouse

Growing marijuana has become much more popular in recent years, increasing the demand for different growing methods. Many growers cultivate their plants outdoors, as it is the easiest way to mimic the plant’s ideal growing environment. However, this is only possible for growers that live in a warm enough climate with plenty of sunlight and a long growing season.

Growers who live in colder climates or who prefer to have control over their plant’s growing conditions often have elaborate indoor growing setups. These can be expensive to maintain and frequently require constant monitoring to ensure nothing fails. There is another option for growers who want the best of both indoor and outdoor growing, and that is growing in a greenhouse.

Many people assume that growing in a greenhouse is reserved for commercial growing practices. However, grow operations of all sizes can benefit from being cultivated in a greenhouse. Below are some of the most common misconceptions about growing marijuana in a greenhouse.

It is not Possible to Grow Cannabis in a Greenhouse in the Winter

Many growers assume that growing cannabis in the winter is impossible, even if it is inside of a greenhouse. However, recent advancements in greenhouse technology have allowed growers to cultivate cannabis even in the frigid cold months of winter.

While the sun does most of the work of heating a greenhouse, some cold climates with a short growing season may need to supplement their heating. This is easy to do with a greenhouse, as growers will only need to do so for part of the day. It is less expensive than heating an indoor grow room and more reliable than growing outdoors.

The Greenhouse Must be Heated All Year in the North

Even in cold climates, greenhouses do not need to be heated all year. This is because greenhouses use the sun to generate heat, even in the colder months. Greenhouses only need supplemental heat periodically to ensure the temperature stays consistent.

Individuals in cold and rainy climates should plan for the weather. For these growers, it may be better to choose a strain of outdoor autoflower seeds to reduce the likelihood of early flowering or hermaphrodite plants. Autoflowering cannabis enters the flowering stage after a set amount of time rather than when the number of light hours is reduced. Typically, these plants are ready to harvest in seven to ten weeks, which may make it easier for growers to stagger the growth of the plants, as well.

The Greenhouse Must be Cooled All Year in the South

Many people assume that growers in southern climates must cool their greenhouses all year, but that is not always the case. In arid regions such as southern California, Arizona, or Western Texas, fan systems are sufficient to manage the temperature of a greenhouse. However, humid climates like Florida, Georgia, or Mississippi will need a more powerful cooling system.

Growers need to plan their greenhouse setup according to their region’s climate. A greenhouse will not be able to reach a temperature that is lower than the air outside without a cooling system.

Dutch Greenhouses are a Necessity for Growing Cannabis

For many people, the first thing that comes to mind when they think of a greenhouse is Dutch Greenhouses. Dutch Greenhouses have been leading the world in greenhouse technology for over one hundred years, so it is easy to see why many people believe this is the best option for growing marijuana.

However, growing cannabis is illegal in the Netherlands. Because of this, their experience with manufacturing greenhouses suitable for cannabis cultivation is limited. U.S. manufacturers have a much stronger reputation for greenhouses used for marijuana.

Growers Must Use Greenhouses Meant for Cannabis

Many greenhouse manufacturers will push the idea that growers must use greenhouses meant for cannabis. Any greenhouse can be used, but using a cookie-cutter greenhouse will not produce the best results. Instead, growers should assess their situation and choose a greenhouse that suits their needs.

Not all greenhouses are created equal. In general, growers should not opt for the cheapest option, as these are usually made with flimsy materials that could leak cold air or allow pests and pathogens into the greenhouse, or the structure may crumble under harsh weather. Instead, i49 growers should opt for a high-quality set up in one of the designs below.

Attached Greenhouse

An attached greenhouse, or a lean-to greenhouse, is built off of the side of a person’s house. Typically, these greenhouses have clear glass windows, so they are not the stealthiest option. However, because growers do not need to go outside before entering the greenhouse, they provide the best protection against infection from outside pests and diseases.

This is an extremely efficient greenhouse design, as the same heat source that the house uses can heat them. Typically, these greenhouses are only large enough to grow two to three plants from sativa seeds, since they give rise to the larger-sized plants. Growers may be able to squeeze a fourth plant into a small greenhouse area like this when growing from indica seeds or choosing fast flowering cannabis strains. These both give rise to shorter and bushier plants which can be pruned for maximal space efficiency.

Detached Greenhouse

Detached greenhouses are their own structure with a wood or metal frame. Growers must be careful to choose a greenhouse that does not use a thick frame, as it will cast a large shadow on the plants inside of it. They are most commonly in the same shape as a house or tunnel, with a pointed or rounded roof that allows precipitation to runoff easily. Since they are not attached to anything, they can be positioned anywhere on a property. The walls can be a frosted or clear plastic or glass, depending on the grower’s preference.

Connected Greenhouse

Connected greenhouses are used predominantly by commercial operations. They are made up of several greenhouses that have been attached to each other, forming a warehouse-style floor plan. These structures maintain a consistent environment throughout the entire grow area but can be expensive to maintain.

Cold Frames

Cold frames are a simple option and are typically smaller and less permanent than other types of greenhouses. These are a favorite of growers with a knack for DIY projects and can be fashioned out of windows, plastic wrapped around a wood frame, and more. Cold frames can be heated by the sun only, so they should not be used by growers in colder climates.


Polytunnels are commonly used in commercial farming but are useful for personal cannabis growers as well. Their frame is made of aluminum bent into a half-circle with a polyurethane sheet fitted onto it. These are a cheap and easily constructed greenhouse, but their cover will need to be replaced periodically. With properly made  retractable poly tunnels, you can allow your afghan kush fem or purple thai strain plants to bask in the open air when the weather is favorable and then shelter them in the event of a major rain or wind storm.

Heating Isn’t Necessary if the Greenhouse has Lights

Lighting is a crucial element to growing cannabis, especially for those growing in a greenhouse during the winter when the sun shines less than 12 hours a day. However, grow lights do not produce adequate heat for growing on their own. Growers must consider supplemental heating options to keep their greenhouse at the ideal ambient temperature.

Cannabis Growers Need a High-Tech Greenhouse if they Want High-Quality Results

While many people invest in high-tech greenhouses for their cannabis plants, that does not ensure they will have high-quality results. Many other factors go into growing a top-notch marijuana plant, including nutrients, pest management, seed or clone quality, and more. Many growers with less advanced greenhouses see excellent results by caring for their plants properly.

A Cannabis Greenhouse is Extremely Expensive to Start

Many growers assume that greenhouses are extremely expensive upfront. While this can be the case for commercial grows, it is not always the most expensive option. Growers who cultivate their sunset sherbert or lemon glue strain plants indoors often have to spend much more money on complicated lighting, heating, and ventilation setups, while greenhouses rely on less expensive things like sunlight, fans, and windows for the same results.

Light Deprivation is a New and Unproven Technology

Proper lighting is essential for growing marijauna seeds into fully budding cannabis plants. Since greenhouses rely heavily on the sun for light, plants that are in the flowering stage when the sun is out for more than 12 hours per day require some form of light deprivation. While this sounds like it requires brand new technology, light deprivation has existed for years. Blackout curtains and other light-blocking methods are used frequently on poinsettias, chrysanthemums, and more.

Growers who Use a Greenhouse can Expect an ROI Within a Year

Some greenhouse manufacturers promise such great results that growers can expect a return on their investment within a year. However, there are too many variables at play when growing cannabis for such claims to be true.

Additionally, many people think growing cannabis is easy, fast money. Unfortunately, that is not the case. Like most industries, there are fluctuations in profitability that mean getting the most out of their investment is not guaranteed within a specific time frame.

The Bottom Line

Growing marijuana plants in a greenhouse is an excellent option for growers with less than ideal outdoor growing conditions or those who want to avoid the cost and maintenance of a complicated indoor growing setup. Greenhouses conserve more energy than indoor grows, protect plants from the dangers of growing outdoors, and allow plants to reach their maximum potential with greater ease.

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